Re: Musk has done good stuff with SpaceX, but...
Putting aside the recent Finnish theory regarding paired photons, we're back to researching Woodward's MET / MEGA Mach effect drives then.
That said, its not just longer-lived probes that would benefit. Station keeping thrusters would still be immensely useful for satellites.
Regardless, I still think both should be getting more effort and funding for research. Even getting a concrete yes or no on whether it works or not is learning something worthwhile. There are after all, worse things we can be spending the money on. Like, F-35s that don't work and worthless politicians. :-P